High resolution MRI techniques have proven to be useable for assessing the anatomy of various blood vessels, including coronary blood vessels, as well as pathological lesions on blood vessel walls. see, Shinnar, M. et al., The Diagnostic Accuracy of Ex Vivo MRI for Human Atherosclerotic Plaque Characterization; Arterioscler. Thromb. Vasc. Biol. 19:2756-2761 (1999) and Hatsukami, T. S., et al., Visualization of Fibrous Cap Thickness and Rupture in Human Atherosclerotic Carotid Plaque In Vivo With High-Resolution Magnetic Resonance Imaging. Circulation 102:959-964 (2000). Also, because MRI is sensitive to changes in temperature, it can be used to assess temperature differences within the body or to monitor heat-based therapies.
The advent of rapid image acquisition sequences has rendered MRI useable as a means for guiding the in vivo positioning of guidewires, catheters and other interventional devices. For example, researchers have devised MRI guidable catheters and guidewires that incorporate MRI antennae and real-time visualization of a guidewire, guiding catheter, and anatomy has been accomplished. See, Serfaty, Jean-Michael, et al., Toward MRI-Guided Coronary Cathetrization: Visualization of Guiding Catheters, Guidewires and Anatomy in Real Time, J. Mag. Reson. Imaging, 12:590-594 (2003). Examples of MRI apparatus (e.g., coils) that may be mounted on or in catheters or other instruments and associated methods to facilitate MRI guidance of such catheters and instruments are described in U.S. Pat. Nos. 5,217,400 (Dumoulin et al.), 5,307,808 (Dumoulin et al.), 6,393,314 (Watkins et al.), 6,332,088 (Zhang et al.), 6,198,962 (Su), 6,198,962 (Su) and 6,171,240 (Young), the entire disclosure of each such United States patent being expressly incorporated herein by reference. One example of a side exit catheter operated using MRI guidance includes United States Patent Application Publication US 2003/32936 (Lederman) entire disclosure expressly incorporated herein by reference. To date, MRI guidance has not yet been used for guidance of tissue penetrating catheters from blood vessels.
In general, tissue penetrating catheters are inserted into blood vessels or other natural or man-made body lumens and advanced to a desired position. A tissue penetrator is then advanced from the catheter to a target location outside of the body lumen in which the catheter is positioned. A substance (e.g., a drug, biologic, cells, filler or other material), device (e.g., a guidewire, catheter, electrode, light guide, substance delivery implant, tool, scope, etc.) or other therapy (e.g., laser, ionizing radiation, etc.) may then be delivered by or through the tissue penetrator to the target location. In some instances the target location may be within the wall of the blood vessel or other luminal anatomical structure in which the catheter is positioned. In other instances, the target location may be another anatomical or pathological structure (e.g., a blood vessel, organ, body cavity, tumor, muscle, nerve, etc.). Examples of tissue penetrating catheter systems and their methods of use include those described in U.S. Pat. Nos. 5,830,222 (Makower), 6,068,638 (Makower), 6,159,225 (Makower), 6,190,353 (Makower, et al.), 6,283,951 (Flaherty, et al.), 6,375,615 (Flaherty, et al.), 6,508,824 (Flaherty, et al.), 6,544,230 (Flaherty, et al.), 6,579,311 (Makower), 6,602,241 (Makower, et al.), 6,655,386 (Makower, et al.), 6,660,024 (Flaherty, et al.), 6,685,648 (Flaherty, et al.), 6,709,444 (Makower), 6,726,677 (Flaherty, et al.) and 6,746,464 (Makower) the entire disclosure of each such United States patent being expressly incorporated herein by referenceImage guidance of tissue penetrating catheters can present unique challenges not associated with other types of catheters. For example, it is sometimes desirable for the operator to be provided with, not only an indication of the catheter's position within the body, but also an indication of the catheter's rotational orientation relative to the target location and/or other indication of the trajectory on which the penetrator will advance. Such indication of catheter rotational orientation and/or penetrator trajectory enables the operator to pre-orient the catheter so that, when the tissue penetrator is subsequently advanced, it will enter the target location and not some other unintended location. Thus, there remains a need in the art for the development of MRI guidable tissue penetrating catheters and related methods of use.